The continued goal of our program is to study the influences of ventilatory non-uniformities on respiratory mechanical function. As a group we tender the hypothesis that classical descriptions of ventilatory mechanics based on single lumped-parameters, such as pulmonary resistance, are inadequate to describe lung function. Instead we assert that a complex structure, such as the lung, needs to be considered by methods that account for its intrinsic asymmetry, non-uniformity, and non-linearity. Project 1 is directed at questions concerning parenchymal function. In Project 1, we will examine dynamic alveolar pressure-volume behavior using laser light scattering stereology and use this information to predict overall parenchymal pressure-volume behavior. Projects 3, 4, 5 and 7, all address airway function. In Projects 3 and 4, the physiological factors influencing gas transport and flows during low volume high frequency oscillation are examined. The influence of both serial and parallel inhomogeneity on gas transport will be determined. Project 5 addresses the question of the uniformity of lung emptying during forced expiratory maneuvers while in Project 7 the fluid dynamics of these basic processes is explored. Project 6 will examine non-uniform respiratory muscle activation. We propose to predict the behavior of the overall ventilatory system based on a knowledge of individual muscle function and mechanical system design. Each of these projects addresses specific issues in respiratory non-homogeneity in a novel way. The combined information should provide new conceptual insights into the non-uniform aspects of ventilatory behavior.